“花环式”海流发电站是由一串螺旋桨组成的，它的两端固定在浮筒上，浮筒里装有发电机。整个电站迎着海流的方向漂浮在海面上，就像献给客人的花环一样。下图为“花环式海流发电站示意图”，读图回答下列各题。

    It's Saturday morning. My parents and I are on a tour bus. There are about twenty people on the bus. Some are from America, and some are from England and Australia. They are all our friends. We are going to the Great Wall. On the bus, there are two Chinese. One is a woman, the other is a man. The woman is good at English. She is talking with us about the Great Wall. The other people are listening to her. They like the Great Wall. They want to see it very much.

如图是无线电广播过程的简易图．话筒把播音员的声音信号转换成电信号，调制解调器把音频信号加载到____ 电流上发射到空中，收音机接收到各种电磁波并从中选出特定频率的信号．通过解调将____ 信号留下，通过扬声器把播音员的声音从收音机播放出来．

饮食与健康密切相关．下列做法中有益于健康的是（　　）